使用php写入linux中的管道

Question

I have created a pipe in linux mkfifo /tmp/myFIFO now i have set the chmod to 777.. then i have ac application which reads the pipe and output what i wrote to the pipe.

When i do it this way in php and this works..

$command = "echo 'helloworld' > myFIFO";
$process = proc_open($command, $descriptor, $pipes, $cwd, $env);

but when i do it with fwrite eg

$out = fopen("/tmp/myFIFO","w");
fwrite($out,"hello");
fclose($out);

It does not work at all. I'm not getting any output from my pipe in linux?.. Why is that fwrite is not working?.. thanks

Answer 1

It's working now thanks for all your help. I set the chmod to a+rw.

chmod a+rw /tmp/myFIFO

Now it's working fine now.

Thanks for all your help.

Answer 2

FIFOs have the strange behavior that when you first open them for writing (either directly with the open(2) system call or via any wrapper such as fopen(3) ), the open call blocks until a reader also opens the same FIFO for reading. When both ends have opened, the two calls are unblocked, and reading and writing can commence.

What you're probably seeing is that your program is never getting to the fwrite call (which should function normally) because the fopen call never returns, since no reader has opened the other end of the FIFO yet. If you have another program open up the FIFO for reading, it should work.